On the bubbling dynamics of binary mixtures of powders in 2D gas-solid fluidized beds

The bubbling behavior of fluidized beds has been thoroughly investigated in the last decades by means of several techniques (e.g. X-ray, Inductance, Resistance and Impedance based techniques). In recent years, Digital Image Analysis Techniques have shown their potential for accurate and cost effective measurements. Most of the works related to the experimental analysis of bubble behavior in the field of gas-solid fluidization actually deal with monodispersed particles although almost all industrial equipments operate with mixtures of particles. Among the works available in literature dealing with mixtures of particles having different diameters and/or densities, most of them aim at the assessment of minimum fluidization conditions and mixing/ segregation phenomena. A lack of knowledge exists in the experimental analysis of bubble properties measurements of polydispersed systems. In this work, a Digital Image Analysis procedure has been applied to the case of binary mixtures of particles in bubbling fluidized beds, in order to measure bubble fundamental characteristics such as bubble diameter, bubble number and bubble rise velocity, i.e. data actually unavailable in the literature. The experiments have been carried out at steady state conditions with binary mixtures of corundum particles and glass particles, at various inlet gas velocities. A preliminary statistical analysis has been performed to describe bubbling dynamics, which may well be a starting point for future development of predictive correlations.